Multi-layer ceramic electronic component

ABSTRACT

A multi-layer ceramic electronic component includes: a ceramic body including a multi-layer unit having a side surface facing in a direction of a first axis and including internal electrodes laminated in a direction of a second axis orthogonal to the first axis and having end portions on the side surface, and a side margin including a first inner layer adjacent to the side surface and including a first region containing a glass component, a first outer layer outside of the first inner layer, and a ridge positioned at an end portion of the first outer layer in the direction of the second axis and including a second region containing a glass component at a lower concentration than a concentration of the glass component of the first region, the side margin having a dimension of 13 μm or less in the direction of the first axis; and an external electrode.

BACKGROUND ART

The present disclosure relates to a multi-layer ceramic electroniccomponent including side margins provided in a later step.

A multi-layer ceramic capacitor includes a protective unit forprotecting the circumference of internal electrodes. For miniaturizationand increase in capacitance of the multi-layer ceramic capacitor, it isadvantageous to thin the protective unit, which does not contribute tothe formation of a capacitance, as much as possible. Japanese PatentApplication Laid-open No. 2015-029123 discloses a technique capable ofthinning the protective unit.

In the technique disclosed in Japanese Patent Application Laid-open No.2015-029123, a multi-layer unit having side surfaces from which internalelectrodes are exposed is produced, and side margins are provided to theside surfaces of the multi-layer unit. In this multi-layer ceramiccapacitor, even if the side margins are thinned to achieve theminiaturization and increase in capacitance, the side margins canappropriately protect the side surfaces of the multi-layer unit, fromwhich the internal electrodes are exposed.

SUMMARY OF THE INVENTION

However, in the multi-layer ceramic capacitor, as the side marginsprovided to the side surfaces of the multi-layer unit become thinner,cracks that occur in the side margins when an external impact is appliedthereto are more likely to reach the side surfaces of the multi-layerunit. Thus, in the multi-layer ceramic capacitor, a short circuit of theinternal electrodes on the side surfaces of the multi-layer unit islikely to occur due to the entry of moisture or the like.

In view of the circumstances as described above, it is desirable toprovide a multi-layer ceramic electronic component capable of obtaininghigh impact resistance even if side margins are thinned.

Additional or separate features and advantages of the disclosure will beset forth in the descriptions that follow and in part will be apparentfrom the description, or may be learned by practice of the disclosure.The objectives and other advantages of the disclosure will be realizedand attained by the structure particularly pointed out in the writtendescription and claims thereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present disclosure, as embodied and broadly described, in oneaspect, the present disclosure provides a multi-layer ceramic electroniccomponent including a ceramic body and an external electrode.

The ceramic body includes a multi-layer unit and a side margin.

The multi-layer unit has a side surface facing in a direction of a firstaxis and includes internal electrodes, the internal electrodes beinglaminated in a direction of a second axis orthogonal to the first axisand having respective end portions positioned on the side surface.

The side margin includes a first inner layer adjacent to the sidesurface of the multi-layer unit and including a first region containinga glass component, a first outer layer positioned outside of the firstinner layer, and a ridge positioned at an end portion of the first outerlayer in the direction of the second axis and including a second regioncontaining a glass component at a lower concentration than aconcentration of the glass component of the first region. The sidemargin has a dimension of 13 μm or less in the direction of the firstaxis.

The external electrode covers the ceramic body from a direction of athird axis orthogonal to the first axis and the second axis.

In this configuration, high sinterability is obtained by an action ofthe glass component in the first inner layer of the side margin. Thiscan ensure high adhesiveness of the side margin to the side surface ofthe multi-layer unit. Meanwhile, the ridge of the side margin, which islikely to receive an external impact in the ceramic body, has a smallamount of glass component and can thus suppress the progress of cracksalong the crystal grain boundary. With this configuration, in themulti-layer ceramic electronic component, high impact resistance isobtained even if the side margin is thinned to have 13 μm or less.

The first outer layer of the side margin may include the second region.

In this configuration, in the entire side margin, the progress of cracksalong the crystal grain boundary can be suppressed.

The multi-layer unit may further include a functional unit including theinternal electrodes, and a cover that covers the functional unit fromthe direction of the second axis.

The cover may include a second inner layer adjacent to the functionalunit and including the first region, and a second outer layer positionedoutside of the second inner layer and including the second region.

In this configuration, also in the cover, the progress of cracks alongthe crystal grain boundary can be suppressed while ensuring highadhesiveness to the functional unit.

An entire region, of an outer surface of the ceramic body, which is notcovered with the external electrode, may include the second region.

In this configuration, in the entire ceramic body, the progress ofcracks along the crystal grain boundary can be suppressed.

The functional unit may include ceramic layers positioned between theinternal electrodes and including the second region.

In this configuration, a decrease in function due to the glass componentin the ceramic layers is less likely to occur, and thus high performanceis easily obtained.

As described above, according to the present disclosure, it is possibleto provide a multi-layer ceramic electronic component capable ofobtaining high impact resistance even if side margins are thinned.

These and other objects, features and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription of embodiments thereof, as illustrated in the accompanyingdrawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory, andare intended to provide further explanation of the disclosure asclaimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a multi-layer ceramic capacitoraccording to an embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of the multi-layer ceramic capacitortaken along the A-A′ line in FIG. 1;

FIG. 3 is a cross-sectional view of the multi-layer ceramic capacitortaken along the B-B′ line in FIG. 1;

FIG. 4 is a cross-sectional view of another configuration example of themulti-layer ceramic capacitor;

FIG. 5 is a cross-sectional view of another configuration example of themulti-layer ceramic capacitor;

FIG. 6 is a flowchart showing a production method 1 for the multi-layerceramic capacitor;

FIGS. 7A, 7B, and 7C are plan views of ceramic sheets, which areprepared in the process of preparing ceramic sheets in the productionmethod 1;

FIG. 8 is a perspective view showing a lamination process in theproduction method 1;

FIG. 9 is a plan view showing a cutting process in the production method1;

FIG. 10 is a perspective view of a multi-layer unit obtained in thecutting process in the production method 1;

FIG. 11 is a perspective view of a ceramic body obtained in the processof forming side margins in the production method 1;

FIGS. 12A and 12B are cross-sectional views showing the process offorming side margins in the production method 1;

FIGS. 13A and 13B are cross-sectional views showing an anotherconfiguration example of the process of forming side margins in theproduction method 1;

FIGS. 14A and 14B are cross-sectional views showing an anotherconfiguration example of the process of forming side margins in theproduction method 1;

FIGS. 15A and 15B are cross-sectional views showing the process offorming side margins in a production method 2 for the multi-layerceramic capacitor; and

FIG. 16 is a cross-sectional view showing an example of a multi-layerceramic capacitor obtained by the production method 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be describedwith reference to the drawings.

In the figures, an X axis, a Y axis, and a Z axis orthogonal to oneanother are shown as appropriate. The X axis, the Y axis, and the Z axisare common in all figures.

1. Configuration of Multi-layer Ceramic Capacitor 10 1.1 OverallConfiguration

FIGS. 1 to 3 each show a multi-layer ceramic capacitor 10 according toan embodiment of the present disclosure. FIG. 1 is a perspective view ofthe multi-layer ceramic capacitor 10. FIG. 2 is a cross-sectional viewof the multi-layer ceramic capacitor 10 taken along the A-A′ line inFIG. 1. FIG. 3 is a cross-sectional view of the multi-layer ceramiccapacitor 10 taken along the B-B′ line in FIG. 1.

The multi-layer ceramic capacitor 10 includes a ceramic body 11, a firstexternal electrode 14, and a second external electrode 15. The ceramicbody 11 is configured as a hexahedron having a pair of end surfacesfacing in the X-axis direction, a pair of side surfaces facing in theY-axis direction, and a pair of main surfaces facing in the Z-axisdirection.

The first external electrode 14 and the second external electrode 15cover both the end surfaces of the ceramic body 11 and face each otherin the X-axis direction while sandwiching the ceramic body 11therebetween. The first external electrode 14 and the second externalelectrode 15 extend to the main surfaces and the side surfaces from theend surfaces of the ceramic body 11. With this configuration, the firstexternal electrode 14 and the second external electrode 15 have U-shapedcross sections parallel to the X-Z plane and the X-Y plane.

It should be noted that the shapes of the first and second externalelectrodes 14 and 15 are not limited to those shown in FIG. 1. Forexample, the first and second external electrodes 14 and 15 may extendto one of the main surfaces from both the end surfaces of the ceramicbody 11 and have L-shaped cross sections parallel to the X-Z plane. Thisconfiguration allows the thickness of the multi-layer ceramic capacitor10 along the Z-axis direction to be kept small.

The first and second external electrodes 14 and 15 are each formed of agood conductor of electricity. Examples of the good conductor ofelectricity forming the first and second external electrodes 14 and 15include a metal mainly containing copper (Cu), nickel (Ni), tin (Sn),palladium (Pd), platinum (Pt), silver (Ag), gold (Au), or the like or analloy of them.

The ceramic body 11 is formed of dielectric ceramics and includes amulti-layer unit 16 and side margins 17. The multi-layer unit 16 has apair of side surfaces S that face in the Y-axis direction. Further, themulti-layer unit 16 has a pair of end surfaces that partially constitutethe end surfaces of the ceramic body 11, and a pair of main surfacesthat partially constitute the main surfaces of the ceramic body 11.

The multi-layer unit 16 has a configuration in which a plurality ofsheet-like ceramic layers 20 extending along the X-Y plane are laminatedin the Z-axis direction. The multi-layer unit 16 includes a capacitanceforming unit 18 and a pair of covers 19. The capacitance forming unit 18is configured as a functional unit having the function of forming acapacitance. The pair of covers 19 covers the capacitance forming unit18 from above and below in the Z-axis direction. The pair of covers 19constitutes the pair of main surfaces of the multi-layer unit 16.

The capacitance forming unit 18 includes first internal electrodes 12and second internal electrodes 13. The first and second internalelectrodes 12 and 13 each have a sheet-like shape extending along theX-Y plane and are laminated along the Z-axis direction. The first andsecond internal electrodes 12 and 13 are alternately disposed along theZ-axis direction between the ceramic layers 20. In other words, thefirst internal electrode 12 and the second internal electrode 13 thatare adjacent to each other face each other in the Z-axis direction whilesandwiching the ceramic layer 20 therebetween.

The first internal electrodes 12 are drawn to the end surface coveredwith the first external electrode 14. Meanwhile, the second internalelectrodes 13 are drawn to the end surface covered with the secondexternal electrode 15. With this configuration, the first internalelectrodes 12 are connected to only the first external electrode 14, andthe second internal electrodes 13 are connected to only the secondexternal electrode 15.

The first and second internal electrodes 12 and 13 are formed over theentire width of the capacitance forming unit 18 in the Y-axis direction.In other words, both end portions of the first and second internalelectrodes 12 and 13 in the Y-axis direction are positioned on the pairof side surfaces S of the multi-layer unit 16. With this configuration,in the ceramic body 11, the positions of both the end portions of thefirst and second internal electrodes 12 and 13 in the Y-axis directionare aligned within the range of 0.5 μm in the Y-axis direction.

A pair of side margins 17 cover the pair of side surfaces S of themulti-layer unit 16, from which both the end portions of the first andsecond internal electrodes 12 and 13 are exposed. With thisconfiguration, the multi-layer ceramic capacitor 10 can ensureinsulation properties between the first internal electrodes 12 and thesecond internal electrodes 13 on the pair of side surfaces S of themulti-layer unit 16 covered with the side margins 17.

In the multi-layer ceramic capacitor 10, the side margin 17, which doesnot contribute to the formation of a capacitance, is formed to have asmall thickness as the dimension in the Y-axis direction. This isadvantageous to a large capacitance and miniaturization of themulti-layer ceramic capacitor 10. Specifically, in the multi-layerceramic capacitor 10, the side margin 17 has a thickness of 13 μm orless.

With such a configuration, when a voltage is applied between the firstexternal electrode 14 and the second external electrode 15 in themulti-layer ceramic capacitor 10, the voltage is applied to the ceramiclayers 20 between the first internal electrodes 12 and the secondinternal electrodes 13. This allows the multi-layer ceramic capacitor 10to store charge corresponding to the voltage applied between the firstexternal electrode 14 and the second external electrode 15.

In the ceramic body 11, in order to increase capacitances of therespective ceramic layers 20 provided between the first internalelectrodes 12 and the second internal electrodes 13, dielectric ceramicshaving a high dielectric constant is used. Examples of the dielectricceramics having a high dielectric constant include a material having aPerovskite structure containing barium (Ba) and titanium (Ti), which istypified by barium titanate (BaTiO₃).

It should be noted that the ceramic layer 20 may have a compositionbased on strontium titanate (SrTiO₃), calcium titanate (CaTiO₃),magnesium titanate (MgTiO₃), calcium zirconate (CaZrO₃), calciumzirconate titanate (Ca(Zr,Ti)O₃), barium zirconate (BaZrO₃), titaniumoxide (TiO₂), or the like.

The first and second internal electrodes 12 and 13 are each formed of agood conductor of electricity. Examples of the good conductor ofelectricity forming the first and second internal electrodes 12 and 13typically include nickel (Ni), and other than nickel (Ni), include ametal mainly containing copper (Cu), palladium (Pd), platinum (Pt),silver (Ag), gold (Au), or the like or an alloy of them.

1.2 Detailed Configuration of Ceramic Body 11 1.2.1 Description ofOutline

The ceramic body 11 includes a first region and a second region thathave microstructures different from each other. Specifically, the firstregion has a microstructure, which contains a glass component andincludes a glass phase deposited in a crystal grain boundary that is aboundary portion of crystal grains. The second region has amicrostructure, which has a lower concentration of the glass componentthan that of the first region and in which the glass phase is notsubstantially deposited in the crystal grain boundary.

The glass component included in the first region only needs to be acomponent that has a low melting point and forms a liquid phase at thesintering of the ceramic body 11. Such a glass component includes, forexample, silicon and boron. In the first region, a liquid phaseincluding the glass component is discharged from the crystal grains atthe sintering, and the glass phase becomes a microstructure resultingfrom the segregation of the glass phase in the crystal grain boundary.

In the first region, the presence of the glass phase having a lowdielectric constant makes it difficult to obtain a large capacitance.Meanwhile, in the second region, a reduction in capacitance due to theinfluence of the glass phase does not occur, which makes it easy toobtain a large capacitance. For that reason, in the multi-layer ceramiccapacitor 10, it is favorable that the plurality of ceramic layers 20constituting the capacitance forming unit 18 constitutes the secondregion.

Further, in the first region in which the glass phase is deposited inthe crystal grain boundary, high sinterability is obtained by thegeneration of the liquid phase at the sintering. Meanwhile, in the firstregion in which the glass phase has a low mechanical strength, a brittlefracture is likely to occur in the crystal grain boundary. In otherwords, in the first region, cracks are likely to occur in the crystalgrain boundary, and the generated cracks are likely to progress alongthe crystal grain boundary.

To the contrary, in the second region in which the glass phase is notsubstantially deposited in the crystal grain boundary, the mechanicalstrength in the crystal grain boundary is high, and thus cracks are lesslikely to occur in the crystal grain boundary and less likely toprogress along the crystal grain boundary. Meanwhile, in the secondregion, since the liquid phase is not substantially generated at thesintering of the ceramic body 11, high sinterability is less likely tobe obtained.

In the ceramic body 11, the arrangement of the first region and thesecond region is determined such that the circumference of thecapacitance forming unit 18 can be appropriately protected and highimpact resistance can be achieved. Hereinafter, as examples of thearrangement of the first region and the second region in the ceramicbody 11, a configuration example 1 shown in FIG. 3, a configurationexample 2 shown in FIG. 4, and a configuration example 3 shown in FIG. 5will be described.

1.2.2 Configuration Example 1

In the configuration example 1 of the ceramic body 11 shown in FIG. 3,each side margin 17 includes a first inner layer 17 a and a first outerlayer 17 b. The first inner layer 17 a is adjacent to the side surface Sof the multi-layer unit 16 and constitutes a bonding surface for theside surface S of the multi-layer unit 16.

The first outer layer 17 b is positioned outside of the first innerlayer 17 a in the Y-axis direction and constitutes the side surface ofthe ceramic body 11.

Each first outer layer 17 b includes a pair of ridges 17 c that extendalong the X-axis direction at both the end portions in the Z-axisdirection. The ridges 17 c have a shape bulging outward and are alsoexposed to the outside at the central regions in the X-axis directionwithout being covered with the first and second external electrodes 14and 15. Thus, the ceramic body 11 is likely to receive a strong impact,particularly from the outside, at the ridges 17 c.

In each figure, the first region is shown in a dense dot pattern, andthe second region is shown in a rough dot pattern. As shown in FIG. 3,in each of the side margins 17 according to the configuration example 1,only the ridges 17 c constitute the second regions, and the first innerlayer 17 a and a portion of the first outer layer 17 b excluding theridges 17 c constitute the first regions. Further, the covers 19according to the configuration example 1 constitute the first regions.

In the first inner layers 17 a and the covers 19, which constitute thefirst regions, high sinterability is obtained. Thus, in the ceramic body11, high adhesiveness of the first inner layers 17 a and the covers 19to the capacitance forming unit 18 can be ensured. Therefore, in theceramic body 11, the circumference of the capacitance forming unit 18 isappropriately protected, and the performance such as moisture resistanceis likely to be maintained.

Further, at the ridges 17 c, which constitute the second regions, themechanical strength in the crystal grain boundary is high, and thuscracks are less likely to occur in the crystal grain boundary even if anexternal impact is received, and cracks are less likely to progressalong the crystal grain boundary. Thus, in the ceramic body 11 accordingto the configuration example 1, the occurrence of cracks that reach thefirst and second internal electrodes 12 and 13 from the surfaces of theridges 17 c can be suppressed also in the configuration including thethin side margins 17.

1.2.3 Configuration Example 2

In the configuration example 2 of the ceramic body 11 shown in FIG. 4,the configuration of the first outer layer 17 b of the side margin 17 isdifferent from the configuration example 1 and is common to theconfiguration example 1 in the other configurations. Specifically, inthe side margin 17 according to the configuration example 2, the wholeof the first outer layer 17 b including the ridges 17 c is configured asthe second region.

In the ceramic body 11 according to the configuration example 2, themechanical strength of the crystal grain boundary is high in the wholeof the first outer layer 17 b constituting the side surface. Thus, inthe ceramic body 11 according to the configuration example 2, theoccurrence of cracks that reach the first and second internal electrodes12 and 13 from the surfaces, which are the second regions, can besuppressed also in the configuration including the thin side margins 17.

1.2.4 Configuration Example 3

In the configuration example 3 of the ceramic body 11 shown in FIG. 5,the configuration of the covers 19 is different from the configurationexample 2 and is common to the configuration example 2 in the otherconfigurations. Each of the covers 19 according to the configurationexample 3 includes a second inner layer 19 a and a second outer layer 19b. The second inner layer 19 a is adjacent to the capacitance formingunit 18. The second outer layer 19 b is positioned outside of the secondinner layer 19 a in the Z-axis direction and constitutes the mainsurface of the ceramic body 11.

In the cover 19 according to the configuration example 3, the secondinner layer 19 a constitutes the first region, and the second outerlayer 19 b constitutes the second region. In the ceramic body 11according to the configuration example 3, the mechanical strength of thecrystal grain boundary is high in the second outer layer 19 b thatconstitutes the main surface, and thus the occurrence of cracks thatreach the first and second internal electrodes 12 and 13 from the mainsurface can be suppressed.

2. Production Method for Multi-layer Ceramic Capacitor 10 2.1 ProductionMethod 1 2.1.1 Description of General Outline

FIG. 6 is a flowchart showing a production method 1 for the multi-layerceramic capacitor 10 according to this embodiment. FIGS. 7A to 14B areviews each showing a production process for the multi-layer ceramiccapacitor 10. Hereinafter, the production method 1 for the multi-layerceramic capacitor 10 will be described along FIG. 6 with reference toFIGS. 7A to 14B as appropriate.

2.1.2 Step S01: Preparation of Ceramic Sheet

In Step S01, first ceramic sheets 101 and second ceramic sheets 102 forforming the capacitance forming unit 18, and third ceramic sheets 103for forming the covers 19 are prepared. The first, second, and thirdceramic sheets 101, 102, and 103 are configured as unsintered dielectricgreen sheets mainly containing dielectric ceramics.

The first, second, and third ceramic sheets 101, 102, and 103 are eachformed into a sheet shape by using a roll coater or a doctor blade, forexample. The thickness of each of the first and second ceramic sheets101 and 102 is adjusted in accordance with the thickness of the ceramiclayer of the sintered capacitance forming unit 18. The thickness of thethird ceramic sheet 103 is adjustable as appropriate.

Further, a glass component is added to the third ceramic sheet 103,which forms the cover 19 to constitute the first region. Meanwhile, aglass component is not added to the first and second ceramic sheets 101and 102, which form the ceramic layers 20 of the capacitance formingunit 18 to constitute the second region.

FIGS. 7A, 7B, and 7C are plan views of the first, second, and thirdceramic sheets 101, 102, and 103, respectively. At this stage, thefirst, second, and third ceramic sheets 101, 102, and 103 are eachconfigured as a large-sized sheet that is not singulated. FIGS. 7A, 7B,and 7C each show cutting lines Lx and Ly used when the sheets aresingulated into the multi-layer ceramic capacitors 10. The cutting linesLx are parallel to the X axis, and the cutting lines Ly are parallel tothe Y axis.

As shown in FIGS. 7A, 7B, and 7C, unsintered first internal electrodes112 corresponding to the first internal electrodes 12 are formed on thefirst ceramic sheet 101, and unsintered second internal electrodes 113corresponding to the second internal electrodes 13 are formed on thesecond ceramic sheet 102. It should be noted that no internal electrodesare formed on the third ceramic sheet 103 corresponding to the cover 19.

The first internal electrodes 112 and the second internal electrodes 113can be formed by applying an optional electrically conductive paste tothe first ceramic sheets 101 and the second ceramic sheets 102,respectively. The method of applying the electrically conductive pasteis optionally selectable from publicly known techniques. For example,for the application of the electrically conductive paste, a screenprinting method or a gravure printing method can be used.

In the first and second internal electrodes 112 and 113, gaps are formedin the X-axis direction along the cutting lines Ly for every othercutting line Ly. The gaps between the first internal electrodes 112 andthe gaps between the second internal electrodes 113 are alternatelydisposed in the X-axis direction. In other words, a cutting line Lypassing through a gap between the first internal electrodes 112 and acutting line Ly passing through a gap between the second internalelectrodes 113 are alternately disposed.

Furthermore, in Step S01, fourth ceramic sheets 104 a and fifth ceramicsheets 104 b (see FIGS. 12A to 14B) for forming the side margins 17 arealso prepared in the manner similar to the above. A glass component isadded to the fourth ceramic sheets 104 a but not added to the fifthceramic sheets 104 b.

2.1.3 Step S02: Lamination

In Step S02, the first, second, and third ceramic sheets 101, 102, and103 prepared in Step S01 are laminated as shown in FIG. 8, to produce amulti-layer sheet 105. In the multi-layer sheet 105, the first ceramicsheets 101 and the second ceramic sheets 102 that correspond to thecapacitance forming unit 18 are alternately laminated in the Z-axisdirection.

Further, in the multi-layer sheet 105, the third ceramic sheets 103corresponding to the covers 19 are laminated on the upper and lowersurfaces of the alternately laminated first and second ceramic sheets101 and 102 in the Z-axis direction. The number of first, second, andthird ceramic sheets 101, 102, and 103 to be laminated can be determinedin accordance with the configuration of the multi-layer ceramiccapacitor 10.

The multi-layer sheet 105 is integrated by pressure-bonding the first,second, and third ceramic sheets 101, 102, and 103. For thepressure-bonding of the first, second, and third ceramic sheets 101,102, and 103, for example, hydrostatic pressing or uniaxial pressing isfavorably used. This makes it possible to obtain a high-densitymulti-layer sheet 105.

2.1.4 Step S03: Cutting

In Step S03, the multi-layer sheet 105 obtained in Step S02 is cut alongthe cutting lines Lx and Ly, to produce unsintered multi-layer units116. Each of the multi-layer units 116 corresponds to a multi-layer unit16 to be obtained after sintering. The multi-layer sheet 105 can be cutwith a push-cutting blade, a rotary blade, or the like.

FIG. 9 is a plan view of the multi-layer sheet 105 after Step S03. Themulti-layer sheet 105 is cut along the cutting lines Lx and Ly while themulti-layer sheet 105 is held by an adhesive sheet C such as a foamedrelease sheet. The multi-layer sheet 105 is cut into pieces in such amanner, and thus the multi-layer units 116 are obtained.

FIG. 10 is a perspective view of the unsintered multi-layer unit 116obtained in Step S03. The multi-layer unit 116 includes an unsinteredcapacitance forming unit 118 and unsintered covers 119. Further, in themulti-layer unit 116, the first and second internal electrodes 112 and113 are exposed from the cut surfaces, i.e., the side surfaces S, andthe end portions of the first and second internal electrodes 112 and 113in the Y-axis direction are aligned with one another on the sidesurfaces S.

2.1.5 Step S04: Formation of Side Margin

In Step S04, unsintered side margins 117 are provided to both the sidesurfaces S of the multi-layer unit 116 obtained in Step S03. With thisconfiguration, an unsintered ceramic body 111 shown in FIG. 11 isobtained. In order to form the side margins 117, the fourth and fifthceramic sheets 104 a and 104 b prepared in Step S01 are used.

In Step S04, a portion to be the first region in the side margin 17 isformed of the fourth ceramic sheet 104 a, and a portion to be the secondregion in the side margin 17 is formed of the fifth ceramic sheet 104 b.FIGS. 12A to 14B are cross-sectional views showing Step S04corresponding to the configuration examples 1 to 3 shown in FIGS. 3 to5, respectively.

In the configuration example 1, as shown in FIG. 12A, the fourth ceramicsheets 104 a corresponding to the first inner layers 17 a are attachedto the side surfaces S of the multi-layer unit 116, and thereto, thefourth ceramic sheets 104 a corresponding to portions of the first outerlayers 17 b excluding the ridges 17 c, and the fifth ceramic sheets 104b corresponding to the ridges 17 c are attached.

With this configuration, an unsintered ceramic body 111 according to theconfiguration example 1 shown in FIG. 12B is obtained. In the unsinteredceramic body 111 according to the configuration example 1, unsinteredside margins 117 each including a first inner layer 117 a, a first outerlayer 117 b, and ridges 117 c, which cover the side surface S of theunsintered multi-layer unit 116, are formed.

In the configuration example 2, as shown in FIG. 13A, the fourth ceramicsheets 104 a corresponding to the first inner layers 17 a are attachedto the side surfaces S of the multi-layer unit 116, and thereto, thefifth ceramic sheets 104 b corresponding to the first outer layers 17 bincluding the ridges 17 c are attached. With this configuration, anunsintered ceramic body 111 according to the configuration example 2shown in FIG. 13B is obtained.

In the configuration example 3, as shown in FIG. 14A, ceramic sheets 103a, to which a glass component is added and which correspond to thesecond inner layers 119 a, and ceramic sheets 103 b, to which a glasscomponent is not added and which correspond to the second outer layers119 b, are used as the third ceramic sheets 103 that form the covers119.

Subsequently, the fourth ceramic sheets 104 a corresponding to the firstinner layers 17 a are attached to the side surfaces S of the multi-layerunit 116, and thereto, the fifth ceramic sheets 104 b corresponding tothe first outer layers 17 b including the ridges 17 c are attached. Withthis configuration, an unsintered ceramic body 111 according to theconfiguration example 3 shown in FIG. 14B is obtained.

2.1.6 Step S05: Sintering

In Step S05, the ceramic body 111 shown in FIG. 11, which is obtained inStep S04, is sintered to produce the ceramic body 11 of the multi-layerceramic capacitor 10 shown in FIGS. 1 to 3. In other words, through StepS05, the multi-layer unit 116 becomes the multi-layer unit 16, and theside margins 117 become the side margins 17.

A sintering temperature in Step S05 can be determined on the basis of asintering temperature for the ceramic body 111. For example, if a bariumtitanate (BaTiO₃) based material is used, the sintering temperature canbe set to approximately 1,000 to 1,300° C. Further, sintering can beperformed in a reduction atmosphere or a low-oxygen partial pressureatmosphere, for example.

In the ceramic body 111 in the process of sintering, sintering isaccelerated in the capacitance forming unit 118 in which the first andsecond internal electrodes 112 and 113 having a low sinteringtemperature are disposed. Meanwhile, in each of the configurationexamples 1 to 3, in the ceramic body 111 in the process of sintering,sintering is accelerated also in the first inner layer 117 a of the sidemargin 117 in which the liquid phase of the glass component isgenerated.

Thus, in the ceramic body 111 in the process of sintering, themismatching in sintering behavior between the capacitance forming unit118 and the first inner layer 117 a of the side margin 117, which havehigh sinterability, is less likely to occur. Therefore, highadhesiveness of the side margin 17 to the capacitance forming unit 18can be ensured in the multi-layer ceramic capacitor 10.

Further, similarly, in each of the configuration examples 1 to 3, in theceramic body 111 in the process of sintering, sintering is acceleratedin a portion adjacent to at least the capacitance forming unit 118 inthe cover 119 due to the generation of the liquid phase of the glasscomponent. Thus, in the multi-layer ceramic capacitor 10, highadhesiveness of the covers 19 to the capacitance forming unit 18 can beensured.

2.1.7 Step S06: Formation of External Electrode

In Step S06, the first external electrode 14 and the second externalelectrode 15 are formed in both the end portions of the ceramic body 11in the X-axis direction obtained in Step S05, to complete themulti-layer ceramic capacitor 10 shown in FIGS. 1 to 3. The method offorming the first external electrode 14 and the second externalelectrode 15 in Step S06 is optionally selectable from publicly knownmethods.

2.2 Production Method 2

In the production method 2 for the multi-layer ceramic capacitor 10according to this embodiment, the configurations shown in Step S04 andStep S05 are different from those in the production method 1, andconfigurations of the other steps are common to those in the productionmethod 1. In the production method 2, in order to form the side margins117, only the fourth ceramic sheets 104 a are used, and the fifthceramic sheets 104 b are not used.

FIGS. 15A and 15B are cross-sectional views showing Step S04 of theproduction method 2. As shown in FIG. 15A, the fourth ceramic sheets 104a are attached to the side surfaces S of the multi-layer unit 116. Itshould be noted that a single fourth ceramic sheet 104 a or a laminateof a plurality of fourth ceramic sheets 104 a may be used for the fourthceramic sheet 104 a. With this configuration, an unsintered ceramic body111 shown in FIG. 15B is obtained.

In the production method 2, the sintering of the ceramic body 111 inStep S05 is performed in a reduction atmosphere. In the ceramic body 111in the process of sintering, sintering is accelerated in a surface layerportion that comes into contact with a reducing gas. Thus, in theceramic body 111 in the process of sintering, the glass component thatis present as a liquid phase in the surface layer portion is dischargedto the inside along with the crystal growth in the surface layerportion.

In Step S05 of the production method 2, sinterability in the surfacelayer portion of the ceramic body 111 can be provided with adistribution depending on sintering conditions. For example, providing astrong reducing atmosphere can selectively improve the sinterability ofthe ridges 117 c that come into contact with the reducing gas from twodirections along the Y axis and the Z axis.

Thus, for example, employing the sintering conditions in which theatmosphere has strong reducibility and a sintering time is short canreduce the concentration of the glass component in only the ridges 17 cin the surface layer portion of the ceramic body 11. With thisconfiguration, only the ridges 17 c become the second regions, and theceramic body 11 according to the configuration example 1 shown in FIG. 3is obtained.

Further, to the contrary, employing the sintering conditions in whichthe atmosphere has weak reducibility and a sintering time is long canreduce the concentration of the glass component in the entire region ofthe surface layer portion of the ceramic body 11. This provides aceramic body 11 in which the entire surface layer portion shown in FIG.16 constitutes the second region having a low concentration of the glasscomponent.

In the multi-layer ceramic capacitor 10 shown in FIG. 16, the entireregion, of the outer surface of the ceramic body 11, which is notcovered with the first and second external electrodes 14 and 15, is thesecond region. This provides a multi-layer ceramic capacitor 10 capableof suppressing the occurrence of cracks that reach the first and secondinternal electrodes 12 and 13 from the outer surface in the entireceramic body 11.

3. Example and Comparative Examples

For each of Example and Comparative examples 1 and 2 of the embodimentdescribed above, 2,000 samples of the multi-layer ceramic capacitorshaving common configurations excluding the side margins were produced.Samples according to Example each have a configuration similar to theconfiguration example 1 shown in FIG. 3. Samples according toComparative examples 1 and 2 have configurations different from theconfiguration example 1 shown in FIG. 3 in the configuration of the sidemargins.

Specifically, in the samples according to Comparative example 1, theentire side margin constitutes the first region, that is, the glassphase is deposited in the crystal grain boundary over the entire sidemargin. In the samples according to Comparative example 2, the entireside margin constitutes the second region, that is, the glass phase isnot substantially deposited in the crystal grain boundary over theentire side margin.

A moisture resistance test was performed for the 1,000 samples of eachof Example and Comparative examples 1 and 2. In the moisture resistancetest, the samples were held for 1,000 hours at a temperature of 85° C.and a humidity of 85% under application of a rated voltage of 4 V.Subsequently, the samples whose electric resistance value was smallerthan 1 MΩ after the moisture resistance test were determined asdefectives due to an insulation failure.

As a result, no defectives were found in any of the samples according toExample and Comparative example 1. On the other hand, defectives werefound in three samples according to Comparative example 2. Consequently,it was determined that the moisture resistance is improved by formingthe first inner layer, which is adjacent to the side surfaces of themulti-layer unit, to be the first region.

Next, an impact resistance test was performed for the 1,000 samples ofeach of Example and Comparative examples 1 and 2. In the impactresistance test, each sample was dropped on a desk from a height of 30cm. Subsequently, visual inspection was performed on the droppedsamples, and samples with cracks were determined as defectives due toinsufficient impact resistance.

As a result, no defectives were found in any of the samples according toExample and Comparative example 2. On the other hand, defectives werefound in two samples according to Comparative example 1. Consequently,it was determined that the impact resistance is improved by forming theridges of the side margins to be the second regions.

4. Other Embodiments

While the embodiment of the present disclosure has been described, thepresent disclosure is not limited to the embodiment described above, andit should be appreciated that the present disclosure may be variouslymodified.

For example, the present disclosure is applicable to not only themulti-layer ceramic capacitor but also a general multi-layer ceramicelectronic component including a functional unit in which a plurality ofinternal electrodes are laminated. Examples of the multi-layer ceramicelectronic component to which the present disclosure is applicableinclude a chip varistor, a chip thermistor, and a multi-layer inductor,in addition to the multi-layer ceramic capacitor.

What is claimed is:
 1. A multi-layer ceramic electronic component,comprising: (a) a ceramic body including: (i) a multi-layer unit having:a side surface facing in a direction of a first axis and including afunctional unit, said functional unit including internal electrodes thatare laminated in a direction of a second axis orthogonal to the firstaxis and have respective end portions positioned on the side surface,and a cover facing and covering the functional unit in the direction ofthe second axis and including a first region which is defined as aregion containing a first concentration of a glass component; and (ii) aside margin including: a first inner layer positioned adjacent to theside surface of the multi-layer unit and including the first regioncontacting the first region of the cover, a first outer layer positionedoutside of the first inner layer, and a ridge positioned at an endportion of the first outer layer in the direction of the second axis andincluding a second region which is defined as a region containing asecond concentration of the glass component which is lower than thefirst concentration of the glass component of the first region, whereinthe side margin has a dimension of 13 μm or less in the direction of thefirst axis; and (b) an external electrode that covers the ceramic bodyfrom a direction of a third axis orthogonal to the first axis and thesecond axis.
 2. The multi-layer ceramic electronic component accordingto claim 1, wherein the first outer layer of the side margin includesthe second region.
 3. The multi-layer ceramic electronic componentaccording to claim 1, wherein the cover includes: a second inner layeradjacent to the functional unit and including the first region; and asecond outer layer positioned outside of the second inner layer andincluding the second region.
 4. The multi-layer ceramic electroniccomponent according to claim 3, wherein an entire region, of an outersurface of the ceramic body, which is not covered with the externalelectrode, includes the second region.
 5. The multi-layer ceramicelectronic component according to claim 1, wherein the functional unitincludes ceramic layers positioned between the internal electrodes andincluding the second region.